A new general method of resolving racemic alcohols and its application to (rs)-2-hydroxy-2-(3-phenoxyphenyl)acetonitrile and (rs)-allethrolone

The preparation is described of pure (S)-2-hydroxy-2-(3-phenoxyphenyl)acetonitrile (the alcohol component of some very active pyrethroids) from the racemic form of this 2-hydroxyacetonitrile. The new resolution process is based on differences in physical properties of two diastereoisomeric ethers. The resolving agents used are chiral hemiacetal compounds; one of these, 4-hydroxy-6,6-dimethyl-3-oxabicyclo[3.1.0]hexan-2-one, is available from an industrial synthesis of chrysanthemic acid, and appears specially useful for a two-step resolution of many racemic alcohols, even base-sensitive types.